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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1977

Aerodynamic behavior of the Viking entry vehicle - Ground test and flight results

An extensive series of tests of the Viking entry vehicle flying in pure CO2 was conducted in a ballistic range at Ames Research Center. The primary purpose of these tests was to calibrate the aerodynamic lift and drag characteristics in order to allow the density, pressure, and temperature profiles of the Martian atmosphere to be determined from onboard instrumentation carried on Viking. Both the Viking 1 and Viking 2 entry vehicles performed flawlessly during entry and descent, and the atmosphere structure was deduced to an altitude of about 120 km. A description is given of the ballistic range tests and of the aerodynamic behavior of the full scale entry vehicles during entry into the Martian atmosphere. Some comparisons between ground test and flight results are shown.

Kirk, D. B.↗
NASA NTRSDate not supplied

Exploring the Accuracy of RANS Simulations for Mars Entry Vehicles

Accurate yet inexpensive predictions of aerodynamic coefficients for Mars entry vehicles have remained a consistent challenge over the past five decades. Below Mach 6, drag on the backshell becomes significant and must be accurately predicted. Steady Reynolds-averaged Navier-Stokes (RANS) models are commonly used, despite their poor predictions of backshell pressure. While scale-resolving simulations have shown promise in the past decade, there is still a need for cheap, accurate RANS predictions for large aerodynamic databases. The Mars Science Laboratory (MSL) is used as a case study to examine predictive accuracy and known shortcomings for RANS predictions of Mars entry vehicles. Several different grid generation techniques are compared, including a comparison between prismatic boundary layer grids and fully unstructured, tetrahedral grids. Comparisons are made to experimental data for Mach 2.5, 3.5, and 4.5. The accuracy of predicted aerodynamic coefficients is examined. Overpredictions in axial force and drag are explained by a closer examination of the surface pressure. These findings document sensitivities and best practices for future RANS database development of Mars entry vehicles.

CFD↗
NASA NTRS2020

Deployable Entry Vehicles for Future Science and Exploration Missions

Deployable Entry Vehicle (DEV) technology has made significant advances over the last decade with ground test development campaigns and flight test demonstrations. DEVs offer benefits over traditional rigid entry vehicles including lower volume and mass, while enabling larger payload delivery and greater landing access. A crucial mission benefit is the DEV capability to transform from a compactly stowed configuration within the launch vehicle to a high drag area entry system for delivery of landers, rovers, aerial platforms, and orbiters (via aerocapture). These benefits span the range of mission classes from Small Satellite (smallsat) to human-class exploration systems. This paper will describe DEV technology development status, highlight mission concepts, and recommend future investments.

Alan Cassell↗
NASA NTRSDate not supplied

Deployable Entry Vehicles for Future Science and Exploration Missions

Deployable Entry Vehicle (DEV) technology has made significant advances over the last decade with ground test development campaigns and flight test demonstrations. DEVs offer benefits over traditional rigid entry vehicles including lower volume and mass, while enabling larger payload delivery and greater landing access. A crucial mission benefit is the DEV capability to transform from a compactly stowed launch configuration to a high drag area entry system for delivery of landers, rovers, aerial platforms, and orbiters (via aerocapture). These benefits span the range of mission classes from Small Satellite to human-class exploration systems. This presentation will describe DEV technology development status, highlight mission concepts, and recommend future investments.

Mission Design↗
NASA NTRS2020

Pterodactyl: Control System Design for Deployable Entry Vehicles

As space exploration missions continue to get more complex, greater demands for mass and volume are being placed on planetary entry vehicles. At the same time, the desire for precision entry targeting to enable surface missions at very specific locations is becoming common. Deployable aeroshells are one type of technology that is being developed to increase the down-mass capability of planetary entry vehicles while complying with current launch vehicle volume constraints. Propulsive control can be used for precision entry targeting but can require a large percentage of the vehicle's total mass or volume for propellant. The Pterodactyl project is studying alternative entry control systems on a Deployable Entry Vehicle to potentially introduce a mass and volume efficient entry system that can achieve precision targeting. This paper presents the mechanical design work undertaken to support the Pterodactyl trade study of three entry vehicle control system options: 1) Flaps, 2) Mass Movement, and 3) Reaction Control System.

D'Souza, Sarah↗
NASA NTRS2019

The Multi-Mission Earth Entry Vehicle for Sample Return Missions – Past, Present, and Future

The Multi-Mission Earth Entry Vehicle (MMEEV) is an enabling technology developed at NASA’s Langley Research Center (LaRC) over the last two decades for returning samples to Earth across a wide array of space science missions. Currently, the MMEEV is being considered for NASA’s Mars Sample Return (MSR) mission. The original vehicle concept, the Earth Entry Vehicle (EEV), was innovated at LaRC in 1998 as a robust solution to return Mars soil samples to Earth under stringent backward contamination requirements. These backward contamination requirements drove the EEV to have higher reliability than any capsule previously designed for a return-to-Earth sample return mission. The EEV achieved this high reliability by employing a passive (no active systems) vehicle architecture optimized for fault tolerance in a compact, low-mass configuration that is extensible to virtually any sample return mission. The original EEV concept utilized a carbon-carbon primary structure with high-density carbon phenolic thermal protection system. The capsule had a 60-degree sphere-cone forebody and a backshell geometry uniquely tailored to produce aerodynamics that would passively re-orient the vehicle if it entered the atmosphere with an off-nominal attitude. Contrary to every other sample return capsule conceived at the time, the EEV was designed to land without a parachute. The vehicle incorporated an integral energy-absorbing crushable structure that protected the Mars sample for landings on surfaces ranging from soft soil to solid concrete. This paper describes 20 years of technological advancements LaRC has incorporated into the EEV architecture to evolve it from the original, MSR-enabling vehicle, to a true multi-mission capability relevant to any sample return mission. The vehicle’s unique Integrated Composite Stiffener Structure (ICoSS) has been optimized for specific strength - supporting high-G atmospheric entries with steep entry angles that produce precise landing footprints on the ground. The vehicle geometry has been refined through wind tunnel testing and computational fluid dynamics simulations to improve the vehicle’s aerodynamic stability and robustness to off-nominal conditions from hypersonic to subsonic flight. The resulting configuration of the current MMEEV architecture is described, with details provided on its sample carrying capacity and atmospheric entry trajectory capabilities. The upgraded vehicle performance is mapped into current space science objectives, showing how the MMEEV supports future sample return missions and continues to be an enabling technology for NASA’s vision to return samples from Mars.

J M Corliss↗
NASA NTRS2008

Limit Cycle Analysis Applied to the Oscillations of Decelerating Blunt-Body Entry Vehicles

Many blunt-body entry vehicles have nonlinear dynamic stability characteristics that produce self-limiting oscillations in flight. Several different test techniques can be used to extract dynamic aerodynamic coefficients to predict this oscillatory behavior for planetary entry mission design and analysis. Most of these test techniques impose boundary conditions that alter the oscillatory behavior from that seen in flight. Three sets of test conditions, representing three commonly used test techniques, are presented to highlight these effects. Analytical solutions to the constant-coefficient planar equations-of-motion for each case are developed to show how the same blunt body behaves differently depending on the imposed test conditions. The energy equation is applied to further illustrate the governing dynamics. Then, the mean value theorem is applied to the energy rate equation to find the effective damping for an example blunt body with nonlinear, self-limiting dynamic characteristics. This approach is used to predict constant-energy oscillatory behavior and the equilibrium oscillation amplitudes for the various test conditions. These predictions are verified with planar simulations. The analysis presented provides an overview of dynamic stability test techniques and illustrates the effects of dynamic stability, static aerodynamics and test conditions on observed dynamic motions. It is proposed that these effects may be leveraged to develop new test techniques and refine test matrices in future tests to better define the nonlinear functional forms of blunt body dynamic stability curves.

Schoenenberger, Mark↗
NASA NTRS2005

Passive Stability on an Entry Vehicle to Enhance Crew Survival

The most desirable crew survival feature for an entry vehicle is probably a full coverage escape system. With full coverage escape, crew survival is maintained for a wide range of failures by the allowing the crew to escape from the failed vehicle and performing the entry to touchdown flight phase in an alternative system. However, there are considerable challenges in providing a separate entry capability, and for some programs, requiring full coverage escape could result in program cancellation. An alternative means of providing for crew survival if the flight control system fails is to design a return vehicle that can enter without active attitude control. A study was performed to assess the feasibility of performing a totally passive entry. Lift over drag has a major impact on performing a passive entry, so a parametric of three typical lift over drag concepts was performed. First an assessment of historical entry vehicles was completed. Second an assessment of end of mission entry trajectories and entry trajectories initiated from ascent abort profiles were made. Trajectories for a wide array of pitch, yaw, and roll rates were made. Third, six-degree-of freedom analyses of the entry were performed. FOP a truly passive return, the entry vehicle must trim in only the heat shield forward orientation. An assessment of the effect of center of gravity placement to achieve this orientation was made.

Deger, Daniel J.↗
NASA NTRS2000

Thermal Analysis Methods for an Earth Entry Vehicle

Thermal analysis of a vehicle designed to return samples from another planet, such as the Earth Entry vehicle for the Mars Sample Return mission, presents several unique challenges. The Earth Entry Vehicle (EEV) must contain Martian material samples after they have been collected and protect them from the high heating rates of entry into the Earth's atmosphere. This requirement necessitates inclusion of detailed thermal analysis early in the design of the vehicle. This paper will describe the challenges and solutions for a preliminary thermal analysis of an Earth Entry Vehicle. The aeroheatina on the vehicle during entry would be the main driver for the thermal behavior. and is a complex function of time, spatial position on the vehicle, vehicle temperature, and trajectory parameters. Thus. the thermal analysis must be closely tied to the aeroheating analysis in order to make accurate predictions. Also, the thermal analysis must account for the material response of the ablative thermal protection system TPS. For the exo-atmospheric portion of the mission, the thermal analysis must include the orbital radiation fluxes on the surfaces. The thermal behavior must also be used to predict the structural response of the vehicle (the thermal stress and strains) and whether they remain within the capability of the materials. Thus, the thermal analysis requires ties to the three-dimensional geometry, the aeroheating analysis, the material response analysis, the orbital analysis. and the structural analysis. The goal of this paper is to describe to what degree that has been achieved.

Amundsen, Ruth M.↗
NASA NTRS2000

Thermal Analysis Methods For Earth Entry Vehicle

Thermal analysis of a vehicle designed to return samples from another planet, such as the Earth Entry vehicle for the Mars Sample Return mission, presents several unique challenges. The Earth Entry Vehicle (EEV) must contain Martian material samples after they have been collected and protect them from the high heating rates of entry into the Earth's atmosphere. This requirement necessitates inclusion of detailed thermal analysis early in the design of the vehicle. This paper will describe the challenges and solutions for a preliminary thermal analysis of an Earth Entry Vehicle. The aeroheating on the vehicle during entry would be the main driver for the thermal behavior, and is a complex function of time, spatial position on the vehicle, vehicle temperature, and trajectory parameters. Thus, the thermal analysis must be closely tied to the aeroheating analysis in order to make accurate predictions. Also, the thermal analysis must account for the material response of the ablative thermal protection system (TPS). For the exo-atmospheric portion of the mission, the thermal analysis must include the orbital radiation fluxes on the surfaces. The thermal behavior must also be used to predict the structural response of the vehicle (the thermal stress and strains) and whether they remain within the capability of the materials. Thus, the thermal analysis requires ties to the three-dimensional geometry, the aeroheating analysis, the material response analysis, the orbital analysis, and the structural analysis. The goal of this paper is to describe to what degree that has been achieved.

Amundsen, Ruth M.↗
NASA NTRS2017

Passive Earth Entry Vehicle Landing Test

Two full-scale passive Earth Entry Vehicles (EEV) with realistic structure, surrogate sample container, and surrogate Thermal Protection System (TPS) were built at NASA Langley Research Center (LaRC) and tested at the Utah Test and Training Range (UTTR). The main test objective was to demonstrate structural integrity and investigate possible impact response deviations of the realistic vehicle as compared to rigid penetrometer responses. With the exception of the surrogate TPS and minor structural differences in the back shell construction, the two test vehicles were identical in geometry and both utilized the Integrated Composite Stiffener Structure (ICoSS) structural concept in the forward shell. The ICoSS concept is a lightweight and highly adaptable composite concept developed at NASA LaRC specifically for entry vehicle TPS carrier structures. The instrumented test vehicles were released from a helicopter approximately 400 m above ground. The drop height was selected such that at least 98% of the vehicles terminal velocity would be achieved. While drop tests of spherical penetrometers and a low fidelity aerodynamic EEV model were conducted at UTTR in 1998 and 2000, this was the first time a passive EEV with flight-like structure, surrogate TPS, and sample container was tested at UTTR for the purpose of complete structural system validation. Test results showed that at a landing vertical speed of approximately 30 m/s, the test vehicle maintained structural integrity and enough rigidity to penetrate the sandy clay surface thus attenuating the landing load, as measured at the vehicle CG, to less than 600 g. This measured deceleration was found to be in family with rigid penetrometer test data from the 1998 and 2000 test campaigns. Design implications of vehicle structure/soil interaction with respect to sample container and sample survivability are briefly discussed.

Kellas, Sotiris↗
NASA NTRSDate not supplied

Pterodactyl: Aerodynamic and Aerothermal Modeling for a Symmetric Deployable Earth Entry Vehicle with Flaps

NASA’s Pterodactyl project has investigated a deployable atmospheric entry vehicle integrated with a flap control system that provides precision targeting during reentry. The control system consists of eight flaps mounted at the edge of a heatshield that can deflect in and out of the flow. An aerodynamic and aerothermodynamic analysis process was developed for preliminary vehicle design and aerodynamic database generation using engineering and CFD tools with varying levels of fidelity. The objective of this analysis was to: 1) understand the inherent aerodynamics, 2) provide an aerodynamics database for stability and control analysis, and 3) provide qualitative and quantitative aeroheating analysis for Thermal Protection System modeling of the flaps. A high fidelity Euler code, Cart3D, was used to resolve complex flow features such as secondary shocks and shock impingement. A wide range of supersonic (Mach 2) and hypersonic Mach numbers (up to Mach 40) were tested with an Earth atmosphere model. A process was developed to utilize the adaptive volume mesh generator utility of the perfect gas model of Cart3D to create meshes with high cell efficiency and numerical stability prior to running a 2nd order accurate solution with a real gas model. High-fidelity aerothermal CFD simulations were performed using US3D to further improve the aerothermal analysis on hypersonic flow around a complex entry vehicle shape including viscosity, chemical reactions of air species, vibrational energy, and catalytic surface reactions. In this process, it was found that the flap control system provided multi-axis control that can be utilized for entry precision targeting. Additionally, the Pterodactyl vehicle can achieve up to a trim L/D of 0.2. Finally, the increased fidelity of the aerothermal heating environments revealed that the shear stress contributes to increasing the heating on the flaps.

Deployable Entry Vehicle↗
NASA NTRSDate not supplied

Pterodactyl: Aerodynamic and Aerothermal Modeling for a Symmetric Deployable Earth Entry Vehicle with Flaps

NASA’s Pterodactyl project has investigated a deployable atmospheric entry vehicle integrated with a flap control system that provides precision targeting during reentry. The control system consists of eight flaps mounted at the edge of a heatshield that can deflect in and out of the flow. An aerodynamic and aerothermodynamic analysis process was developed for preliminary vehicle design and aerodynamic database generation using engineering and CFD tools with varying levels of fidelity. The objective of this analysis was to: 1) understand the inherent aerodynamics, 2) provide an aerodynamics database for stability and control analysis, and 3) provide qualitative and quantitative aeroheating analysis for Thermal Protection System modeling of the flaps. A high fidelity Euler code, Cart3D, was used to resolve complex flow features such as secondary shocks and shock impingement. A wide range of supersonic (Mach 2) and hypersonic Mach numbers (up to Mach 40) were tested with an Earth atmosphere model. A process was developed to utilize the adaptive volume mesh generator utility of the perfect gas model of Cart3D to create meshes with high cell efficiency and numerical stability prior to running a 2nd order accurate solution with a real gas model. High-fidelity aerothermal CFD simulations were performed using US3D to further improve the aerothermal analysis on hypersonic flow around a complex entry vehicle shape including viscosity, chemical reactions of air species, vibrational energy, and catalytic surface reactions. In this process, it was found that the flap control system provided multi-axis control that can be utilized for entry precision targeting. Additionally, the Pterodactyl vehicle can achieve up to a trim L/D of 0.2. Finally, the increased fidelity of the aerothermal heating environments revealed that the shear stress contributes to increasing the heating on the flaps.

Deployable Entry Vehicle↗
NASA NTRS2001

Integrated Thermal Response Tool for Earth Entry Vehicles

A system is presented for multi-dimensional, fully-coupled thermal response modeling of hypersonic entry vehicles. The system consists of a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), a commercial finite-element thermal and mechanical analysis code (MARC), and a high fidelity Navier-Stokes equation solver (GIANTS). The simulations performed by this integrated system include hypersonic flow-field, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the ablating and charring heatshield material is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of both the heatshield and the structure can be obtained simultaneously. Representative computations for a proposed blunt body earth entry vehicle are presented and discussed in detail.

Chen, Y.-K.↗